I. Field of the Invention
The present invention relates to blind riveting systems.
II. Description of the Prior Art
There are many previously known blind riveting systems which are used primarily in industrial applications. Such systems typically comprise a rivet gun having an internal fluid chamber. A piston is mounted within this fluid chamber which divides the fluid chamber into a drive chamber and a return chamber.
The shank of a blind rivet is then inserted into an opening in the gun while the head of the rivet is inserted into registering openings in the parts to be fastened together. Actuation of the gun fluidly connects the drive chamber in the gun to a source of pressurized incompressible fluid, such as hydraulic fluid, which drives the piston from its forward position towards its retracted position. Simultaneously, a puller assembly attached to the piston grasps the shank of the blind rivet and pulls this shank into the interior of the bore. In doing so, the head of the blind rivet expands and secures the parts together. The movement of the piston to its retracted position also breaks the shank from the blind rivet and this now separated shank is removed to a collection area by a vacuum system.
Following the fastening of the blind rivet, the trigger on the rivet gun is released. Upon release, the return fluid chamber in the rivet gun is fluidly connected with a source of pneumatic pressure which then returns the piston to its forward position in preparation for a subsequent blind riveting operation.
These previously known blind rivet guns have generally used hydraulic or air pressure to drive the piston from its forward to its retracted position and thus perform the blind riveting operation. Likewise, these previously known blind riveting systems have generally utilized pneumatic or a spring pressure to return the piston in the gun to its forward position in preparation for a subsequent blind riveting operation. Such blind riveting systems, however, have suffered from several disadvantages.
One disadvantage of these previously known blind riveting systems is that the shanks separated from the blind rivet can become jammed in the gun upon separation of the shank from the head of the rivet. Furthermore, when this happens, the pneumatic pressure utilized to return the piston to its forward position in preparation for a subsequent riveting operation is insufficient to overcome the jammed shank in the gun. Consequently, when this happens, some disassembly of the gun is required in order to clear the jam and allow continued operation of the gun.
A still further disadvantage of these previously known blind riveting systems is that, since pneumatic or spring pressure is utilized to return the piston from its retracted to its forward position, the pneumatic pressure must necessarily pump the hydraulic fluid in the drive chamber back to its source. While conventional shop pressure is normally sufficient to return the piston from its retracted to its forward position, the return cycle time is relatively slow. This adversely effects the overall operating cycle time of the blind riveting system.